Poor band conditions … or Murphys Law

To be honest …  I don’t know if its the band conditions or a poor coax line…

The  clusters are telling me its band conditons but… I have been having trouble every time the snow falls or it rains heavy with the SWR drastically changing so…

Whats your guess???

Now seeing that last winter I did not have this trouble and all I did was change feed lines …. My first guess would be the feed line…  However just to confuse things a bit more….

Z100F

Last winter I was also using my LDG Autotuner which is no longer in my possession so its just a thought but…  perhaps I am just noticing  the SWR changing more as I have to manually tune the antenna if the SWR goes above the 3:1 that the internal tuner in the FT 450 can handle…

For my Non Amateur Readers–> SWR ( Standing Wave Ratio ) The antenna should be tuned for the lowest SWR .  This can be done my physically adjusting the antenna or using a tuner (matching box device) to electrically change the SWR by adding or removing resistance.

So…

Many amateur radio operators consider any impedance mismatch a serious matter.[3] Power loss will increase as the SWR increases. For example, a dipole antenna tuned to operate at 3.75 MHz—the center of the 80 meter amateur radio band—will exhibit an SWR of about 6:1 at the edges of the band. However, if the antenna is fed with 250 feet of RG-8A coax, the loss due to standing waves is 2.2dB, which may seem like a small loss, but is on a logarithmic scale. If running a typical 100W transmitter on the HF band, 2.2dB of loss would reduce the output power to 60W. That is a 40% reduction in power.

So now back to my problems..

I decided to replace the 50 feet of RG8X coax that had served me well over the last year with a 30 foot run of RG8 coax which was a bit newer and not been outside in the elements on a regular basis.  Normally it was only used when a 2nd antenna was needed for a special event…  Since then my antenna matching has changed every time the weather changes… As this problem did not happen before the coax change I will guess coax…  Although the balun (matching transformer) might of suddenly decided to fail….  first guess is till the coax….  Its fairly easy though as the antenna is fed by coaxial cable from the transmitter to the balun which then connects to the antenna.

S9_43_vertical

The antenna is 43 feet of wire supported by a telescopic mast….  This narrows down what could be wrong to really either the feedline or the 4:1 balun.

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Now some of you more scientific types out there might jump in with numerous theories of whats causing my problems and you might be right…  However I will test out the changes last made first before I start tearing things apart…  Its easier to swap out a feed line…

Now also as they (The Weather Network) are predicting some nasty weather in the next couple of days I have to do this sooner than later.  Also while in the back yard I will also have to re-tarp up the Electric Vespa as I just uncovered it on Friday and went out for a ride…  But now it looks like I should re cover it before the freezing rain and snow hits…

I’ll let you know how the changes work out later today…

I guess Murphy was right…

73bob

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